1. Field of the Invention
The present invention generally relates to prism sheets and liquid crystal display devices using the prism sheet.
2. Discussion of the Related Art
FIG. 6 represents a typical liquid crystal display device 100. The liquid crystal display device 100 includes a housing 11 and a plurality of lamps 12 are above a base of the housing 11. The liquid crystal display device 100 further includes a light diffusion plate 13, a prism sheet 10, and a liquid crystal display panel 15 stacked on the housing 11 in that order. An interior of the housing 11 is configured for reflecting light towards the light diffusion plate 13. The light diffusion plate 13 includes a plurality of dispersion particles. The dispersion particles are configured for scattering light, and thereby enhancing the uniformity of the received light emitting from the light diffusion plate 13.
The prism sheet 10 includes a base layer 101 and a prism layer 102 formed on the base layer 101. The prism layer 102 has a plurality of V-shaped protrusion 103. Each V-shaped protrusion 103 extends along a direction parallel to one edge of the prism sheet 20. The plurality of V-shaped protrusions 103 are regularly and periodically arranged parallel to each other. Typically, a method of manufacturing the prism sheet 10 includes following steps. Firstly, a melted ultraviolet-cured transparent resin is coated on the base layer 101, then the melted ultraviolet-cured transparent resin is solidified to form the prism layer 102.
In use, light emitted from the lamps 12 enters the prism sheet 10 after scattered in the diffusion plate 13. The light is refracted by the V-shaped protrusions 103 of the prism sheet 10 and is thereby concentrated, so that a brightness of light illumination is increased. Finally, the light propagates into an LCD panel 15 disposed above the prism sheet 10.
However, it is prone to occur moire pattern interference effect on the LCD panel 15 due to the V-shaped structures 102 are aligned similarly to the LCD pixels. In order to decrease the moire pattern interference effect, the liquid crystal display device 100 should further include an upper light diffusion film 14 inserted between the prism sheet 10 and the LCD panel 15. Although the upper light diffusion film 14 and the prism sheet 10 are in contact with each other, a plurality of air pockets still exist at the boundary therebetween. When the liquid crystal display device 100 is in use, light passes through the air pockets, and some of the light undergoes total reflection at one or another of the corresponding boundary. In addition, an amount of light is absorbed by the upper light diffusion film 14. As a result, a light brightness of the liquid crystal display device 100 is reduced.
What is needed, therefore, is a new prism sheet and a liquid crystal display device using the prism sheet that can overcome the above-mentioned shortcomings.